That could have sooo many reasons. "Berlin Municipal Airport" does come before "Flughafen Berlin Brandenburg" in the alphabet.
But.. looking for "London", 2 of the first 3 airports are in North America and arguably a lot of people would not count any of the first 5 (Lydd, Oxford & Southend) as London. Heathrow doesn't show up at all without specifying further.
There's a few other areas where the text is suspect, e.g the international airport for Bali, in Denpasar won't show up in searches for Bali (colloquial name of the airport) or Denpasar (city referenced by the IATA code) both of which work in regular flight search, but requires entering the airport codes or its formal name Ngurah Rai. Extra confusion as there is a tiny airport called Bali Airport in Cameroon which shows up instead...
In theory, they could build a system which returns relevant airports ranked by size in terms of latest/peak passenger traffic figures
addr:city=Denpasar
aeroway=aerodrome
iata=DPS
icao=WADD
name=Bandar Udara Internasional Ngurah Rai
name:de=Internationaler Flughafen Ngurah Rai
name:en=Ngurah Rai International Airport
name:fr=Aéroport International Ngurah Rai
name:ko=응우라라이공항
operator=PT. Angkasa Pura I
short_name=Bandara Internasional Ngurah Rai
type=civil
wikidata=Q1061846
wikipedia=id:Bandar Udara Internasional Ngurah Rai
How do these peripheral airports get to name themselves in such a misleading way? 'London Oxford airport' isn't even in Oxford; locals still call it Kidlington airport.
But.. looking for "London", 2 of the first 3 airports are in North America and arguably a lot of people would not count any of the first 5 (Lydd, Oxford & Southend) as London. Heathrow doesn't show up at all without specifying further.